Maths question

Suppose you work with a 8-bit (binary) computer (that is, numbers are represented by a binary word of 8 bits). Reserving one bit each for the sign of the normalised mantissa, the sign of the exponent and the exponent itself, explain to how many significant figures you can represent numbers (not using a hidden bit). What is the smallest positive number you can represent and what is the biggest? How many numbers can be represented in this way? How big must a number be for this computer to overflow?